India's NSE Nifty index has risen 24.4 percent since Sept. 13 when Narendra Modi was declared as BJP's prime ministerial candidate, with overseas funds pumping over $14 billion in Indian cash shares over that period.

"We acknowledge that there is the potential for massive long-term upside, but we suspect that there needs to be further economic pain before the agenda for more fundamental reform to governance practices becomes clearer," Deutsche said in a report on Thursday.

Deutsche says Mexico and China have also witnessed similar selloff in the past as reform euphoria in both markets waned, while Modi's comparison with Margaret Thatcher raises short to medium term risks.

The investment bank says it still prefers India to the other BRICs, but advises non-emerging market investors to wait for a better buying opportunity.